There are 4 handles, each one for a different measuring range:
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.080" to 1/4" (2-6mm) Heads use 54-567-350-BT Handle
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1/4" to 3/4" (6-20mm) Heads use 54-567-375-BT Handle
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3/4" to 4" (20-100mm) Heads use 54-567-400-BT Handle
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4" to 12" (100-300mm) Heads use 54-567-480-BT Handle